A hennin is like a fancy hat that ladies used to wear a really long time ago. It looks kind of like a tall cone with a pointy top and usually has a veil that covers the face. The hennin was very popular in the 14th and 15th centuries in Europe. It was worn by noblewomen to show off their fancy clothes and hairdos. Some hennins were so tall that they had to be supported by wire or sometimes even a frame. The shape and height of the hennin changed over time, and sometimes it was decorated with jewels or even feathers. Nowadays, people don't wear hennins anymore, but you might see them in historical films or at medieval fairs.